The disclosures of the following priority applications and Laid-open patent publications are herein incorporated by reference:
Japanese Patent Application No. 2002-016971 filed Jan. 25, 2002
Japanese Patent Application No. 2002-040223, filed Feb. 18, 2002
Japanese Laid-open Patent Publication No. H 05-142614
Japanese Laid-open Patent Publication No. H 07-261234
Japanese Laid-open Patent Publication No. H 10-213832
Japanese Laid-open Patent Publication No. 2000-039640.
1. Field of the Invention
The present invention relates to a vibration detection device that detects a vibration caused by a hand movement or the like and a vibration correcting optical device internally provided with a vibration detection device.
2. Description of the Related Art
A primary cause of vibrations to which optical devices such as binoculars and photographing apparatuses such as cameras are subjected is unsteady handling by the user. As a means for correcting an image vibration or an image blur caused by such hand movement, vibration correcting optical devices have been proposed in the related art.
The following is an explanation of the operation of a vibration correcting optical device in the related art, given in reference to FIG. 12.
FIG. 12 is a block diagram showing the basic structure adopted in a vibration correcting optical device which includes a vibration detection device.
An angular speed sensor 10, which detects a vibration applied to the vibration correcting optical device, is generally constituted of a piezoelectric vibration-type angular speed sensor capable of detecting coriolis force. An output from the angular speed sensor 10 is transmitted to a reference value calculation unit 52. The reference value calculation unit 52 is a component that calculates a vibration reference value based upon the output from the angular speed sensor 10. After the reference value is subtracted from the vibration signal output by the angular speed sensor 10, the vibration signal is transmitted to an integrating operation unit 54. The integrating operation unit 54 is a component that converts the vibration signal expressed in angular speed units to a vibration angle for the vibration correcting optical device through a time integration executed on the vibration signal.
A target drive position calculation unit 56 calculates target drive position information for a blur correcting lens 80 by incorporating information such as the lens focal length with the information indicating the vibration angle obtained by the integrating operation unit 54. A drive signal arithmetic operations unit 58 calculates the difference between the target drive position information and position information indicating the current position of the blur correcting lens 80 and supplies a drive current to a coil 73 so as to drive the blur correcting lens 80 in conformance to the target drive position information.
A drive unit 70 that drives the blur correcting lens 80 includes an actuator portion that generates a drive force and a position detection sensor portion that detects the position of the blur correcting lens 80.
The actuator portion of the drive unit 70 is constituted of a yoke 71, a magnet 72 and the coil 73. The coil 73 is provided within a magnetic circuit formed by the yoke 71 and the magnet 72, and as a current is supplied to the coil 73, a force is generated at the coil 73 in accordance with Fleming""s left-hand rule. The coil 73 is mounted at a lens barrel 82 housing the blur correcting lens 80. Since the blur correcting lens 80 and the lens barrel 82 are adapted to move along a direction perpendicular to an optical axis I, the blur correcting lens 80 can be driven along the direction perpendicular to the optical axis I by moving the coil 73.
The position detection sensor portion of the drive unit 70, which monitors the movement of the blur correcting lens 80, includes an infrared light emitting diode (hereafter referred to as an IRED) 74, a slit plate 76 having a slit 76a and a PSD (position sensitive device) 77.
Light emitted by the IRED 74 first passes through the slit 76a where the width of the light beam is constricted, and then reaches the PSD 77. The PSD 77 outputs a signal corresponding to the position of the light received on its light receiving surface. Since the slit plate 76 is mounted at the lens barrel 82, the movement of the blur correcting lens 80 is translated to movement of the slit 76a, which, in turn, is translated to movement of the light on the light receiving surface of the PSD 77. Thus, the position of the light received on to the light receiving surface of the PSD 77 is equivalent to the position of the blur correcting lens 80. A signal output by the PSD 77 is fed back as a position signal 78.
This type of vibration correcting optical device is effective for correcting an image blur attributable to an inadvertent hand movement of the user during, for instance, a normal photographing operation performed by the user holding the camera still. However, the camera may not always be used in a stationary state. For instance, the camera may be used by a photographer who often takes pictures by panning the camera or the camera may often be used by a photographer aboard a vehicle such as a helicopter. In addition, during a photographing operation performed with an AF camera, the composition is often modified due to AF lock after the photographic focus is set on a primary subject with the AF function. Since a camera is used in a variety of operating conditions, as described above, a vibration correcting system that can be effectively used under the varying circumstances is much needed.
The following are the requirements for a vibration correcting optical device used under various conditions.
(requirement 1) Under any circumstances, the quality of the image resulting from a photographing operation (the image quality of the picture) is superior to the quality of an image with no vibration correction.
(requirement 2) The user observing a viewfinder image does not experience any discomfort. Namely, during a photographing operation performed by holding the camera in a stationary state or performed from a vehicle, the photographer is able to verify that the vibration correction is in effect (the image appears still), whereas the photographer is able to follow the subject with ease during a panning photographing operation.
In order to meet these requirements, Japanese Laid-open Patent Publication No. H 05-142614, Japanese Laid-open Patent Publication No. H 07-261234, Japanese Laid-open Patent Publication No. H 10-213832 and Japanese Laid-open Patent Publication No. 2000-039640, for instance, propose methods for distinguishing an intended movement from an inadvertent vibration and for classifying movements into specific types (the photographer is holding the camera in the normal manner, the photographer is panning the camera, the photographer is taking pictures from a vehicle, etc.).
However, these vibration correcting optical devices in the related art do not always operate as intended by the photographer. For instance, a relatively large vibration occurring while the photographer is aboard a vehicle sometimes causes an erroneous judgment that the photographer is performing a panning photographing operation.
There is a vibration correcting optical device that allows the photographer to switch vibration correction modes through a switch operation so as to ensure that the vibration correcting optical device is always able to operate as intended by the photographer under various conditions. In this vibration correcting optical device, a different switch position is selected depending upon whether or not the camera is used for a panning photographing operation, and an automatic detection of a panning photographing operation is disallowed if the camera is not used for a panning photographing operation. However, the following problems arise when a vibration correcting optical device assumes such switch settings.
Even when the photographer is performing a normal photographing operation, he may handle the camera as in a panning photographing operation in order to search for the right composition (in order to modify the composition). However, since the switch setting at which a panning photographing operation is automatically detected is not selected for a normal photographing operation, a change in the composition results in an unnatural movement of the image and the image does not stabilize immediately after the composition is selected.
In addition, the result of the photographing operation is adversely affected (the image is blurred) in the worst-case scenario.
If the camera is operated by selecting a switch setting while the composition is being modified and selecting another switch setting after the composition has been decided upon in order to address this problem, the camera operation becomes impracticably complicated.
It is also required of a blur correcting optical system that it be capable of efficiently distinguishing a movement intended by the user, an unintentional vibration and a state in which both intended movements and unintended vibrations occur together.
The present invention, therefore, provides a vibration detection device that is capable of detecting vibrations accurately and efficiently and a vibration correcting optical device that is capable of correcting a vibration as appropriate.
The vibration correcting optical device according to the present invention comprises a vibration detection unit that detects a vibration of the vibration correcting optical device and outputs a vibration detection signal corresponding to the vibration; a vibration state judgment unit that judges a state of the vibration of the vibration correcting optical device to be one of at least three states, based upon the vibration detection signal; an image vibration correcting optical system that corrects an image vibration caused by the vibration of the vibration correcting optical device; a drive unit that drives the image vibration correcting optical system based upon a drive signal; a drive signal arithmetic operation unit that calculates the drive signal based upon the vibration detection signal and outputs the drive signal to the drive unit; and a drive signal calculation control unit that controls a method for calculating the drive signal adopted at the drive signal arithmetic operation unit in conformance to the state of the vibration ascertained through a judgment executed by the vibration state judgment unit.
In the vibration correcting optical device, it is preferred that the device further comprises a reference value calculation unit that obtains through an arithmetic operation a reference value to be used as a reference in processing the vibration detection signal based upon the vibration detection signal, wherein the vibration state judgment unit judges the state of the vibration of the vibration correcting optical device based upon the vibration detection signal and the reference value; and the drive signal arithmetic operation unit calculates the drive signal based upon the vibration detection signal and the reference value.
It is preferred that the vibration state judgment unit judges the state of the vibration to be one of three states, i.e., a normal vibration state, a first abnormal vibration state and a second abnormal vibration state. In this connection, it is preferred that the vibration state judgment unit judges the state of the vibration to be the normal vibration state if the vibration contains a vibration which is not accompanied by a movement of the vibration correcting optical device, judges the state of the vibration to be the first abnormal vibration state if the vibration contains a vibration accompanied by a movement of the vibration correcting optical device and a vibration with a frequency equal to or exceeding a predetermined value and judges the state of the vibration to be the second abnormal vibration state if the vibration contains a vibration accompanied by a movement of the vibration correcting optical device and a vibration with a frequency lower than the predetermined value. Alternatively, it is preferred that the vibration state judgment unit judges the state of the vibration to be the normal vibration state if the vibration is predominantly constituted of a vibration not intended by the photographer, judges the state of the vibration to be the first abnormal vibration state if the vibration is constituted of both a movement intended by the photographer and an unintended vibration and judges the state of the vibration to be the second abnormal vibration state if the vibration is predominantly constituted of a movement intended by the photographer. Further alternatively, it is preferred that the device further comprises a mode switch that can be operated to switch a control state of the drive signal calculation control unit, wherein: the drive signal calculation control unit implements control on the drive signal arithmetic operation unit so that the drive signal, which enables the vibration correcting optical system to correct image vibration, is calculated by the drive signal arithmetic operation unit regardless of a setting selected at the mode switch or whether or not a photographing exposure operation is in progress, if the vibration state judgment unit judges the state of the vibration to be the normal vibration state.
It is preferred that the vibration correcting optical device further comprises a mode switch that can be operated to switch to a state of control implemented by the drive signal calculation control unit, wherein: the drive signal calculation control unit implements control for adjusting the method for calculating the drive signal in conformance to a setting selected at the mode switch. In this connection, it is preferred that at the mode switch, a first mode, in which the control implemented by the drive signal calculation control unit is automatically switched in conformance to the state ascertained through the judgment executed by the vibration state judgment unit and a second mode, in which the drive signal calculation control unit is controlled so as to enable the vibration correcting optical system to correct image vibration regardless of the state ascertained through the judgment executed by a vibration state judgment unit or whether or not a photographing exposure operation is in progress, can be selected. It is further preferred that the vibration state judgment unit judges the state of a vibration to be one of three states, i.e., a normal vibration state, a first abnormal vibration state and a second abnormal vibration state; and the drive signal calculation control unit controls the method for calculating the drive signal adopted at the drive signal arithmetic operation unit so as not to correct image vibration during a photographic exposure preparation but to correct image vibration during a photographing exposure operation, if the vibration state judgment unit judges the state of the vibration to be the first abnormal vibration state and the first mode is selected at the mode switch. Alternatively, it is preferred that the vibration state judgment unit judges the state of a vibration to be one of three states, i.e., a normal vibration state, a first abnormal vibration state and a second abnormal vibration state; and the drive signal calculation control unit controls the method for calculating the drive signal adopted at the drive signal arithmetic operation unit so as to disallow image vibration correction by stopping drive of the vibration correcting optical system regardless of whether or not a photographing exposure operation is in progress, if the vibration state judgment unit judges the state of the vibration to be the second abnormal vibration state and the first mode is selected at the mode switch.
It is preferred that the drive signal calculation control unit implements control so as to switch the method for calculating the drive signal adopted at the drive signal arithmetic operation unit in conformance to whether or not a photographing exposure operation is in progress.
A vibration detection device according to the present invention comprises a vibration detection unit that detects a vibration of a vibration detection target device mounted with the vibration detection device and outputs a vibration detection signal in correspondence to the vibration; a reference value calculation unit that obtains through an arithmetic operation a reference value to be used as a reference in processing the vibration detection signal based upon the vibration detection signal; a movement start detection unit that detects a start of a movement of the vibration detection target device by comparing the vibration detection signal with the reference value; a movement end detection unit that detects an end of the movement of the vibration detection target device by comparing the vibration detection signal with the reference value; and a movement state judgment unit that judges a state of the movement of the vibration detection target device during a period elapsing between the start and the end of the movement of the vibration detection target device and outputs results of the judgment on the movement state. The movement state judgment unit judges the movement state by using the vibration detection signal and the reference value if the vibration detection signal and the reference value satisfy a predetermined condition, and judges the movement state without using the vibration detection signal or the reference value if the vibration detection signal and the reference value do not satisfy the predetermined condition.
In the vibration detection device, it is preferred that the movement state judgment unit holds current judgment results without depending upon the vibration detection signal or the reference value if the vibration detection signal and the reference value do not satisfy the predetermined conditions.
It is preferred that the movement state judgment unit calculates a value representing a difference between the vibration detection signal and the reference value; assigns the predetermined condition in relation to the difference value by mandating that the difference value be within a predetermined range; judges the movement state by using the vibration detection signal and the reference value if the difference value is outside the predetermined range; and judges the movement state without using the vibration detection signal or the reference value if the difference value is within the predetermined range. In this connection, it is preferred that when the vibration detection signal and the reference value are expressed in units of degrees/sec, the predetermined range is xc2x1(0.4 through 0.6) degrees/sec.
It is preferred that the movement state judgment unit judges the state of the movement of the vibration detection target device to be a first movement state which contains a vibration not intended by a user using the vibration detection target device to a predetermined extent or more, or a second movement state which contains a movement intended by the user to a predetermined extent or more, and outputs either the first movement state or the second movement state as movement state judgment results. In this connection, it is preferred that the movement state judgment unit monitors a sign attached to a value representing a difference between the vibration detection signal and the reference value when judging the movement state by using the vibration detection signal and the reference value and sets the movement state judgment results to the second movement state if the sign remains unchanged over a predetermined length of time or longer. Further, it is preferred that the predetermined length of time is {fraction (1/7)} through ⅓ sec. Alternatively, it is preferred that the movement state judgment unit monitors a sign attached to a value representing a difference between the vibration detection signal and the reference value when judging the movement state by using the vibration detection signal and the reference value and sets the movement state judgment results to the first movement state if the sign changes a predetermined number of times or more. It is further preferred that the movement state judgment unit initializes the movement state judgment results if the movement start detection unit detects a movement start so that the movement state judgment results are initialized to the first movement state if an absolute value of a difference between the vibration detection signal and the reference value is smaller than a predetermined value and the movement state judgment results are initialized to the second movement state if the absolute value of the difference is greater than the predetermined value.
It is further preferred that the movement state judgment unit initializes the movement state judgment results if the movement start detection unit detects a movement start.
Another vibration correcting optical device according to the present invention comprises: a vibration detection device according to claim 12; an image vibration correcting optical system that corrects image vibration caused by a vibration of the vibration correcting optical device constituting the vibration detection target device; a drive unit that drives the image vibration correcting optical system; a drive signal arithmetic operation unit that calculates a drive signal based upon the vibration detection signal and the reference value and outputs the drive signal; and a drive signal calculation control unit that controls a method of an arithmetic operation adopted at the drive signal arithmetic operation unit in conformance to results of a detection executed by the movement start detection unit, results of a detection executed by the movement end detection unit and the movement state judgment results obtained at the movement state judgment unit.